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# Gravity and Energy

## Introduction

we are going to identify one of the forces which produces acceleration in all objects on the surface of the Earth irrespective of their mass.

## The Universal Law of Gravitation or Newton's Law of Gravitation

Sir Issac Newton gave a mathematical relation to calculate the force of gravitation and this relation is known as the universal law of gravitation.

## Newton's Third Law of Motion

whenever a force is acting on an object, it produces acceleration in it. The gravitational force of attraction produces acceleration both in the Earth and in the stone.

## Falling Objects and Acceleration due to Gravity

The objects which move towards the Earth due to force of gravity are called freely falling objects.

## Expression for Acceleration due to Gravity

The acceleration produced in a body moving against gravity is also 9.8 m/s2 but oppositely directed therefore g = - 9.8 m/s2.

## Equations of Motion for a Body Moving under Gravity

The motion of a body under gravity is a uniformly accelerated motion and hence all the equations of motion for uniformly accelerated motion along a straight line is applicable to the motion of bodies under gravity.

## Apparent Weight in Space

A body becomes conscious of the weight, whenever its weight is opposed by some other object.

## Density

The density of a substance remains the same under certain specified conditions. Thus the density of a substance is one of its characteristic properties and this property can be used to determine the purity of any substance.

## Relative Density of a Substance

The density of a substance or an object, we find out the mass and volume of the substance.

## Thrust and Pressure

We have defined the force as an external agent, which changes the direction of motion, speed or shape of the body. All along we were discussing only about the forces acting at a point on a body.

## Buoyancy and Archimedes' Principle

It is a matter of common experience that bodies appear lighter when immersed in water or any other liquid.

## Summary

Is the object which moves towards the Earth due to force of gravity.